01 - Bring a large pot of salted water to a boil. Cook spaghetti according to package directions until al dente. Reserve 1/2 cup pasta water, then drain.
02 - While pasta cooks, combine avocados, spinach, basil, garlic, pine nuts, Parmesan, lemon juice, and olive oil in a food processor. Season with salt and pepper.
03 - Blend until smooth and creamy, scraping down sides as needed. Add 1-2 tablespoons pasta water if too thick to reach desired consistency.
04 - Toss drained spaghetti with pesto, adding splash of reserved pasta water as needed to coat noodles evenly.
05 - Serve immediately topped with extra Parmesan, fresh basil leaves, and cracked black pepper.